Yielding Post of Thin Sheet Metal and Method of Arranging Street Lighting

ABSTRACT

Street lighting is positioned with lamp posts of sheet metal that have a round or polygonal cross-section and one or more longitudinal welded joints ( 17 - 20; 24 ). Posts are used that have one longitudinal welded butt joint with a weld that covers only a part of the sheet metal thickness and the posts are positioned so that this joint is directed towards the traffic.

TECHNICAL FIELD

The invention relates to yielding posts of sheet metal that have a round or polygonal cross-section and one or more longitudinal welded joints. The invention also relates to a method of arranging street lighting with yielding posts.

BACKGROUND OF THE INVENTION

Lamp posts along roads shall now be yielding and decelerate a colliding vehicle over a fairly long distance. This is achieved if the posts bend backwards over the vehicle, so that the entire post is deformed when the vehicle continues forwards. Conical posts are known from WO 2008/127168 that are roll-formed and have a welded longitudinal joint. Such roll-formed posts can be produced from such a small sheet metal thickness that they bend on collision in spite of being very sturdy against wind forces. Tall posts have such a large diameter at the bottom, however, that they can offer undesirably great resistance before they bend.

OBJECT OF THE INVENTION

An object of the invention is to ensure that the post bends backwards when run into. Another object is to make the production of the post simpler and faster and more reliable.

BRIEF DESCRIPTION OF THE INVENTION

According to the invention, posts are used that have a longitudinal welded butt joint with a weld that is thinner than the sheet metal thickness and the posts are positioned so that this joint is directed towards the traffic. The invention is defined by

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the cross-section of a lamp post as an example of the invention.

FIG. 2 shows the circled part of FIG. 1 enlarged.

FIG. 3 shows another example of the invention in cross section.

DESCRIPTION OF THE EXAMPLE SHOWN OF THE INVENTION

FIG. 1 shows a lamp post composed of several tapering metal sheets 11-14, which means that the post tapers conically upwards. The sheets can be flat, but can also have longitudinal folds 15,16. The sheets are joined together by longitudinal welded joints 17-20. FIG. 2 shows the joint 17 enlarged. The edges of the opposing sheets 11,12 have bevels 21,22, so that the contact surfaces of the edges are smaller than the sheet metal thickness and are welded together, preferably by laser welding, so that the thickness of the butt welds 23 across the sheet is smaller than the sheet metal thickness. Thus the welds do not cover the whole sheet metal thickness. They should cover at most ¾ of the sheet metal thickness, i.e. have a thickness t₁ less than ¾ of the sheet metal thickness t₂ and they thereby form weaknesses that give way easily if they are run into directly and allow the post to be flattened out and bend in the desired manner, but the welds are sufficiently strong not to constitute weaknesses in relation to wind forces. By making a weld that does not cover the sheet metal thickness, the welding can be carried out faster and still be more reliable. The current can be reduced and altogether, the production will be faster at a reduced cost.

FIG. 3 shows a post that is roll formed from one piece so that it has only one longitudinal joint 24 that is executed in the manner described with reference to FIG. 2. The post has been roll formed in thin sheet metal with a sheet metal thickness of 1-2 mm, e.g. 1.5 mm, and it has a number of areas 25 with stiffening folds with threefold sheet metal in the manner described in WO 2008/127168, to which reference is made. The stiffened areas 25 are strong against wind forces but allow the post to be flattened in the event of crash loading. If the post has a polygonal cross-section, the stiffenings 25 can expediently be formed as corners as shown, but the post can alternatively have a circular cross-section.

The corners stiffened against wind forces are deformed more easily in the event of crash loading than the other corners in the polygonal cross-section and the joint 24 can expediently be executed in one of the corners stiffened against wind forces. Lamp posts according to FIG. 3 should be placed along the road so that the joint 24 is directed towards the traffic.

Posts according to FIG. 1 have so many joints that they do not necessarily need to be positioned with a joint directly facing the traffic. There are always one or two of the joints that are directed towards the traffic, regardless of the rotary position of the posts in relation to the traffic. A roll-formed post according to FIG. 3 can also be roll formed in several parts and like the example in FIG. 1 have several longitudinal welds. 

1. Yielding post of thin sheet metal with a polygonal or round cross-section with at least one longitudinal welded butt joint (17-20,24), wherein the weld (23) has a smaller thickness across the sheet metal than the sheet metal thickness.
 2. Post according to claim 1, wherein the weld (23) has a thickness of less than ¾ of the sheet metal thickness.
 3. Post according to claim 1, wherein the edges (21,22) facing the weld are bevelled.
 4. Post according to claim 1, wherein the weld (23) is a laser weld.
 5. Post according to claim 1, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic.
 6. Post according to claim 5, wherein the lighting post is roll formed and has only one longitudinal joint (24).
 7. Method of arranging street lighting with lamp posts of sheet metal that have a round or polygonal cross-section and one or more longitudinal welded joints (17-20; 24), wherein posts are used that have one longitudinal welded butt joint (17-20; 24) with a weld (23) that has a smaller thickness across the sheet metal than the sheet metal thickness and the posts are positioned so that this joint is directed towards the traffic.
 8. Method according to claim 7, wherein posts are used with a laser welded joint with a weld thickness of less than ¾ of the sheet metal thickness.
 9. Method according to claim 8, wherein posts are used that are roll formed in one piece so that they have only one longitudinal joint (24).
 10. Post according to claim 2, wherein the edges (21,22) facing the weld are bevelled.
 11. Post according to claim 10, wherein the weld (23) is a laser weld.
 12. Post according to claim 3, wherein the weld (23) is a laser weld.
 13. Post according to claim 2, wherein the weld (23) is a laser weld.
 14. Post according to claim 13, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic.
 15. Post according to claim 12, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic.
 16. Post according to claim 11, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic.
 17. Post according to claim 10, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic.
 18. Post according to claim 4, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic.
 19. Post according to claim 3, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic.
 20. Post according to claim 2, wherein it is a lighting post by the road and has a longitudinal welded joint (17-20, 24) directed towards the traffic. 